Silicone elastomer particles have been used for purposes of providing a smooth or soft feeling to cosmetics, providing a natural finish of cosmetics by scattering light, concealing pores of skin and wrinkles and thickening or stabilizing an oil phase by absorbing oil. Examples of the cosmetics include makeup cosmetics such as foundations and makeup bases, base cosmetics such as creams and milky lotions, and sunscreen cosmetics and cleansing cosmetics.
Silicone elastomer particles can be easily added to aqueous cosmetics or oil-in-water type cosmetics by the use of an aqueous dispersion of the silicone elastomer particles. However, water resistance is often needed for cosmetics such as foundations, sunscreen cosmetics, makeup bases and concealers and, therefore, silicone elastomer particles need to be added in non-aqueous type or water-in-oil type cosmetics. In this case, it is known that the silicone elastomer particles are added in a form of powder.
Japanese Patent Application Laid-Open No. Sho-62-243621 (Patent Literature 1) describes a method of dispersing a curable silicone oil in water with a surfactant and curing it to prepare an aqueous dispersion of silicone elastomer particles and, then, removing water to obtain spheric silicone elastomer particles. Japanese Patent Application Laid-Open No. Sho-62-257939 (Patent Literature 2) describes a method of spray drying an aqueous dispersion of silicone elastomer particles comprising a surfactant to obtain silicone elastomer particles. According to this method, spheric silicone elastomer particles having a low tendency for agglomeration can be easily obtained.
A surfactant used for the preparation of an aqueous dispersion of silicone elastomer particles needs to have a high emulsifying ability. Therefore, a polyoxyethylene alkyl phenyl ether with an alkyl group having 8 to 9 carbon atoms or a polyoxyethylene alkyl ether with an alkyl group having 12 to 13 carbon atoms are usually used. For instance, the surfactant, a polyoxyethylene alkyl ether, in Patent Literature 1 has an alkyl group having 12 carbon atoms. Further, a polyoxyethylene alkyl phenyl ether in Patent Literature 2 has an alkyl group having 8 carbon atoms. Japanese Patent Application Laid-Open No. Hei-11-293111 (Patent Literature 3) describes an aqueous dispersion of silicone elastomer particles, comprising a polyoxyethylene alkylether, where at least 10 weight of the alkyl groups in the polyoxyethylene alkylether has 13 carbon atoms and, therefore, a suspension of cured silicone granules having a narrow particle size distribution is provided with a small amount of a surfactant.
Use of an ionic surfactant was proposed. For instance, Japanese Patent Application Laid-Open No. Hei 11-140191 (Patent Literature 4) describes that an aqueous dispersion of silicone elastomer particles comprising both of a nonionic surfactant and an ionic surfactant improves its storage stability. Japanese Patent Application Laid-Open No. 2002-235004 (Patent Literature 5) describes that an aqueous dispersion of silicone elastomer particles comprising an amphoteric surfactant with an alkyl group having 11 to 17 carbon atoms improves its dispersibility in cosmetics.
However, polyoxyethylene alkyl phenyl ethers have such a problem that their decomposition products have the endocrine disturbance and, therefore, are being to be avoided in cosmetics. Ionic surfactants cause strong irritation on a skin, and, therefore, are being to be avoided in cosmetics which stay on skin for a long time, such as, in particular, basic cosmetics, makeup cosmetics and sunscreen cosmetics. Further, polyoxyethylene alkyl ethers with a smaller number of carbon atoms in alkyl groups cause irritation on a skin, and, therefore, are avoided sometimes in cosmetics.
Japanese Patent Application Laid-Open No. 2003-12929 (Patent Literature 6) describes an aqueous dispersion of silicone elastomer particles, comprising polyoxyethylene sorbitan monolaurate. Sorbitan fatty acid ester type surfactants have low irritation on a skin, but have less ability for emulsifying curable silicone oils.
Japanese Patent Application Laid-Open No. 2003-183501 (Patent Literature 7) describes an aqueous dispersion of silicone elastomer particles, comprising polyoxyethylene alkylether with an alkyl group having 16 carbon atoms, and that the use of an adduct of an oxyethylene to an alcohol having 16 carbon atoms as a surfactant, can provide an emulsion which has good stability and less bad influence to a human body, and offer good dispersibility for cosmetics.